Many different noises pollute the environment of a vehicle. Some are due to the tires. In this type of noise, one part of the noise spectrum that is of particular nuisance is the cavity mode. The cavity mode is the resonance of the column of air inside the tire.
The frequency range of the interior noise in a vehicle, which results from a tire when traveling, typically is 80 to 500 Hz. The frequency of the cavity mode is a function of the size of the tire. At very low speed, a peak in the first cavity mode (FCM) is around 230 Hz.
When traveling, two peaks appear. At 80 km/h, the frequencies of these peaks are approximately 210 and 250 Hz. FIG. 1 clearly shows these frequencies (arrow A). From a subjective point of view of comfort, the peaks in the FCM are a nuisance as they are very audible.
It is known that placing mobile components inside a tire may have a positive effect on reducing the interior noise, in particular a damping of the first cavity mode. European patent document EP 1 214 205 B1 clearly illustrates this principle. For example, particles of open-cell materials may be placed in the tire cavity.
U.S. Pat. No. 6,343,843 discloses a pneumatic tire, which is provided with lawn-like materials for damping air resonance of the tire cavity.
Alternatively, filling the cavity with foam or another material, such as sand, is presented in US Patent Application Publication No. 2001/0004924.
U.S. Pat. No. 4,252,378 describes an arrangement in which the rim of a tire is filled with a foam.
European patent document EP 1 510 366 A1 describes an arrangement in which a noise-damping body is placed under a crown zone of a tire.
German patent document DE 102 20 194 describes a tire that includes an absorbent wall placed in an inner cavity of the tire, bonded to two beads of the tire but not bonded elsewhere to an inner wall of the tire. This absorbent wall includes microperforations for damping an air resonance of the tire cavity and a valve to allow inflation and deflation of the tire.
The preceding systems are complex and expensive.